PURPOSE: To provide a leakage detecting system of a gas pipe arrangement capable of detecting leakage of a gas in a gas pipe arrangement from a gas meter to each of gas appliances at any time as required and of quickly detecting a leakage point even when the gas pipe arrangement has complicated branches.

CONSTITUTION: A leakage detecting system of a gas pipe arrangement comprises a group of whistle devices 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, 7i which are respectively disposed a plurality of positions along a gas flow passage in a gas pipe arrangement 3 from a gas meter 2 to a gas range 6 via a boiler 4 and a gas stove 5 and generate detection sounds each of which has a prescribed frequency different from each other corresponding to the respective disposed positions by gas flows. It further comprises a portable detection unit 14 having a microphone 13 that collects the detection sounds that those whistles generate, and determining a pipe arrangement area A-F having a gas leakage based on an electric signal of the microphone to display and alarm.